# Identification of the MADS-Box Gene Family and Development of Simple Sequence Repeat Markers in Chimonanthus praecox

## TL;DR

This study identifies MADS-box genes and develops SSR markers in Chimonanthus praecox, a winter-blooming ornamental plant, to better understand its growth and support breeding efforts.

## Contribution

The study reports the first identification of MADS-box genes and development of SSR markers in Chimonanthus praecox.

## Key findings

- 74 MADS-box genes were identified and mapped across 11 chromosomes in C. praecox.
- Eighty SSR loci were detected, with dinucleotide repeats being most common in Type II MADS genes.
- Ten polymorphic SSR markers were developed and validated for clustering C. praecox cultivars into three distinct groups.

## Abstract

Chimonanthus praecox, a traditional ornamental plant in China, is admired for its ability to bloom during the cold winter season and is recognized as an outstanding woody cut flower. MADS-box genes encode transcription factors essential for plant growth and development, with key functions in regulating flowering time and the formation of floral organs. In this study, 74 MADS-box genes (CpMADS1–CpMADS74) were identified and mapped across 11 chromosomes, with chromosome 1 harboring the highest number (13 genes) and chromosome 3 the fewest (3 genes). Physicochemical property analysis revealed that all CpMADS proteins are hydrophilic and predominantly nuclear-localized. Phylogenetic analysis classified these genes into Type I and Type II subfamilies, highlighting a clear divergence in domain structure. Eighty simple sequence repeat (SSR) loci were detected, with dinucleotide repeats being the most abundant, and the majority located in Type II MADS genes. From 23 C. praecox samples, 10 polymorphic SSR markers were successfully developed and PCR-validated, enabling a cluster analysis that grouped these cultivars into three distinct clusters. This study offers significant insights into the regulation of flowering, floral organ development, genetic linkage map construction, and the application of marker-assisted selection in C. praecox.